Korma was actually designed to be used to do exactly that: write SQL. You don't have to use any of the ORM-y features and you're essentially just writing SQL in a lisp syntax. The advantage, as others have said, is simply composability, which leads to reusable SQL parts.
It's up to you whether you use korma to "just write SQL" or you use the magic :)
Absolutely, and I completely grant you that there are projects where the composability is a huge win. The library looks great, by the way.
I just think a lot of people will have a kneejerk reaction to use something like this because they have a distaste for raw SQL, rather than a considered analysis of the pros and cons.
Because there are cons - every time you use something like this, however well designed, you introduce another layer of abstraction into your software, one that is bound to have some leaks. Maybe it's justified, maybe it isn't.
Just do the analysis to see if this can benefit you, instead of avoiding SQL by default just because it's SQL.
It's up to you whether you use korma to "just write SQL" or you use the magic :)